Heat-resistant exhaust manifold and method of preparing same

ABSTRACT

A method of lining an exhaust manifold is disclosed, including applying a thin layer of a heat-resistant compound to the interior of an exhaust manifold; and bonding the compound to the manifold. The manifold may be in two or more sections when the compound is applied and the sections may subsequently be joined together to form the manifold. The compound may contain zirconium and/or may be a ceramic material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to heat-resistant exhaust manifolds andmethods of preparing such manifolds. More particularly, the presentinvention relates to a method of lining an exhaust manifold with aheat-resistant compound containing zirconium, a ceramic material, orboth, and a heat-resistant manifold which is the product of thedescribed process.

2. Prior Art

In the automotive industry, it has long been recognized that heatgenerated by the combustion process emanating from the exhaust manifoldsinto the engine compartment of a vehicle is a problem. Not only doessuch heat degrade the various components in the engine compartment whichare not heat resistant, but the heat also causes the exhaust manifoldsthemselves to become brittle and deteriorate. The problem is exacerbatedin today's smaller engine compartments since cars are being"down-sized", especially when a high-performance engine is packedtightly into such a small engine compartment, e.g., a turbocharged orsupercharged engine. Heat loss from exhaust manifolds is not limited tosuch high-performance engines, however.

Many varied types of heat shields and insulation have been employed inthe prior attempts to alleviate this problem. Ongoing efforts continueto channel the maximum possible amount of heat which has been generatedin the combustion chambers, from the exhaust ports of the cylinder headsout into and through the exhaust system, minimizing the amount which isreleased in the engine compartment.

Another reason for wishing to channel the maximum amount of heatpossible through the exhaust system is that by retaining heat in theexhaust system, "light off" of the catalytic converter may be achievedsooner if more heat is conveyed directly to the converter. This promotesgreater fuel efficiency as well as lowered exhaust emissions, which areboth high priorities in today's market.

SUMMARY OF THE INVENTION

The present invention provides a method of lining an exhaust manifold,comprising the steps of:

(a) applying a heat-resistant compound to form a first liner on theinside of a first sheet/metal shell, the first shell comprising a firstsection of an exhaust manifold;

(b) bonding the first liner to the first shell;

(c) applying a heat-resistant compound to form a second liner on theinside of a second sheet-matal shell, the second shell comprising asecond section of the exhaust manifold and being alignable with thefirst section;

(d) bonding the second liner to the second shell; and

(e) joining the first and second shells together in an alignedconfiguration to form an exhaust manifold or a portion thereof.

The manifold may be in two or more sections when the compound is appliedthereto, and the parts may be welded or otherwise joined together afterthe compound has been bonded to the manifold. The compound may beapplied in a molten state and may be bonded to the manifold by theapplication of heat thereto. The compound may be a ceramic material, maycontain zirconium, or may contain both of these. The application of thecompound and the heat binding may be performed substantiallysimultaneously. The surface to be coated may be treated to roughen thesurface before the compound is applied, and in one embodiment thecompound is applied in a layer about 10 to about 15 thousands of an inchin thickness.

The present invention also encompasses a heat-resistant manifold whichis prepared by the process of the present invention. Further detailregarding preferred embodiments of the present invention may be found inthe detailed description section. Throughout the following descriptionand in the drawings, identical reference numbers are used to refer tothe same or a similar component shown in multiple figures of thedrawings, in which;

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded perspective view of of an exhaust manifold inaccordance with the present invention;

FIG. 2 is a cross-sectional view of the lower section of the manifold ofFIG. 1; taken along the line 2--2;

FIG. 3 is a view similar to FIG. 2 showing a heat-resistant compoundbeing applied to the interior of the manifold;

FIG. 4 is a cross-sectional view of a section of the assembled manifoldshowing a liner formed of heat-resistant material on the inside thereof.

FIG. 5 is a cross-sectional view of the head of a plasma-arc spray gun,partially cut away.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, four sections of an exhaust manifold body areillustrated, along with additional components of the manifold. Theadditional components shown are a first flange 38 for the attachment ofan exhaust pipe, and a machined plate 39 having holes therein forattachment to a cylinder head of an automotive engine, and may be addedto this manifold body once the heat resistant compound has been bondedthereto and the component parts have been joined together. Theadditional components may be attached to the manifold body by laserwelding, tig welding, or other suitable method. Additional platessimilar to 39 would be used to complete the manifold of FIG. 1.

The manifold illustrated in FIG. 1 comprises a pair of upper sections10, 12 including a first section 10 of a manifold which is a first sheetmetal shell. The manifold of FIG. 1 also includes a pair of lowersections 11, 13 of a manifold including a second section 11 which is asecond sheet metal shell. The first and second sections 10, 11 arealignable as may be seen in FIG. 1.

As shown in FIG. 2, the second section 11 has a ridge 14 formed on eachside of the shell 11 for joining the sections 10, 11 together as will bedescribed herein.

Referring to FIG. 3, a metal spraying gun 15 is illustrated incross-section, applying a thin heat-resistant layer to the inside of theshell 11 forming a liner 16 on the inside thereof. In a metal sprayingapplication a suitable fuel mixture, such as hydrogen, acetylene, oracetylene and oxygen is fed into a fuel inlet 20 of the metal-sprayinggun 16 from a fuel source (not shown). Air is fed into an air port 18 ofthe gun 15, and mixes with the fuel at the outlet 28 of the gun. Thefuel is ignited to form a flame front 30 at the outlet of the gun.

Drive air is applied to a drive air port 22 and passes through a driveair conduit 24 to force a compound in the form of a powder out from areservoir 32 and into a powder conduit 26 and thence into the gun 15.The compound 34 is sprayed outwardly from the gun in a conical patternand is bonded to the inside of the sheet metal shell 11 to form a firstliner 16 on the inside thereof.

The interior surface 9 of the sheet metal shell 11 may be roughenedbeforehand to promote bonding to the surface 9, such as by sandblasting,machining, or other appropriate method. Alternatively, any appropriateadhesive may be applied to the inner surface 11 of the sheet metal shellto promote bonding of the compound 34 to the inside surface 9 of thesheet metal shell 11.

As seen in FIG. 5, an alternate means of applying the compound 34 to thesheet metal shells is plasma-arc spraying. In plasma-arc spraying, a gassuch as nitrogen or argon is fed into a plasma spray gun at a gas inlet47 and passed between two electrodes 40, 41 where it is ionized by acontinuous high voltage arc 42 passing between the electrodes. Thisionizes the gas and forms it into a plasma capable of attainingtemperatures of 20,000° F. or more. The electrodes 40, 41 are normallyliquid cooled by cooling ports 46, 44 to prolong their life. A powder 34which is used to form the heat-resistant liner 16 is fed into the gun 48at a powder inlet 43 and enters the plasma downstream of the arc 42where it is melted by the plasma and is caught up therein and sprayedfrom the outlet 46 of the gun 48 and applied to the inside of themanifold sections 10, 11, 12, 13. Plasma-arc spraying is relatively wellknown and understood in the art.

The compound 34 which is used to form the liner may contain zirconium,may be a metallic alloy or a ceramic material or may be a powderedglassy compound such as zircon. These compounds are used because oftheir known heat-resistant properties. The liner 16 may be bonded to theinterior 9 of the sheet metal shell 11 by the application of heatthereto. While the thickness of the liner 16 is not critical to thepresent invention, a thickness of about 0.010 inches to about 0.015inches has been found to be helpful in promoting heat-resistance in thefinished manifold. Each of the remaining sections 10, 12 and 13 of themanifold is treated in a similar fashion, and the gun 16 or 48 is usedto spray a thin layer of the heat-resistant compound 34 on the insidesthereof, which is bonded to the shells 10, 12, 13 to form similarliners.

Referring to FIG. 4, a cross-sectional view of part of the assembledmanifold is illustrated with the upper section 10 joined to the lowersection 12. The rib 14 of the lower section 11 is bent in a die (notshown) in two operations and is clamped around the ridges 19 of thesheet metal shell 10 and may be welded thereto as at 36 to insure thatexhaust gas will not leak out of the manifold at the seams proximate theridges 14. The ridges 14 thus provide a means for securing the firstsection 10 to the second section 12 in the aligned configuration.Alternative methods of joining the two sections 10, 11 may be used, aswill be appreciated by those skilled in the art. The third and fourthsections 12, 13 are joined together in a similar fashion. The plates 38and 39 are added on as shown in FIG. 1 and three additional platessimilar to 39 would be used to complete the manifold of FIG. 1.

The foregoing description is intended to be illustrative, and notrestrictive. Many modifications of the present invention will occur tothose skilled in the art. All such modifications within the scope of theappended claims are intended to be within the scope and spirit of thepresent invention.

Having, thus, described the invention, what is claimed is:
 1. A methodof lining an exhaust manifold, comprising the steps of:(a) applying aheat-resistant compound to form a first liner on the inside of a firstsheet-metal shell, the first shell comprising a first section of anexhaust manifold; (b) bonding the first liner to the first shell; (c)applying a heat-resistant compound to form a second liner on the insideof a second sheet-metal shell, the second shell comprising a secondsection of the exhaust manifold and being alignable with the firstsection; (d) bonding the second liner to the second shell; and then (e)joining the first and second shells together in an aligned configurationto form an exhaust manifold or a portion thereof.
 2. The method of claim1, wherein the compound is applied in a molten condition and is allowedto solidify in the shells.
 3. The method of claim 2, wherein thecompound is applied by plasma-arc spraying.
 4. The method of claim 1,wherein the liners comprise a ceramic material.
 5. The method of claim1, wherein the liners comprise zirconium.
 6. The method of claim 1,wherein the steps are performed substantially simultaneously.
 7. Themethod of claim 1, further comprising the step of roughening theinteriors of the shells prior to applying the compound.
 8. Aheat-resistant exhaust manifold which is a product of the method ofclaim
 1. 9. The manifold of claim 8, wherein the liners comprisezirconium.
 10. The manifold of claim 8, wherein the liners comprise aceramic material.
 11. A heat-resistant exhaust manifold, comprising:(a)a first section of a manifold body formed in a sheet metal shell; (b) asecond section of a manifold body formed in a sheet metal shell andbeing alignable with the first section; (c) a thin liner for each of thefirst and second sections, the liners bonded to the respective sections;and (d) means for securing the first section to the second section in analigned configuration.